Oklahoma Highway Patrol's lake patrol division was testing new sonar equipment last week in Foss Lake in Custer County, Okla., when they detected some unusual echoes that indicated the presence of large, metal objects under the water.

"Our guys just naturally assumed this may have been a stolen car pushed off into the lake. Sometimes that happens," Randolph said. "As soon as they pulled up the first vehicle, they found a femur bone in the driver's seat."

Three feet away, they found a second car with more skeletal remains in it. They have since recovered six skulls and matching bones.

Randolph did not know how far from the shore the cars were but said there is a concrete ramp on the edge of the lake for people to back their boats into the water.

Investigators believe they might have some leads on the identities of the people in the cars, possibly solving cold cases from more than 40 years ago.

"Missing persons reports from 1969 and 1970 that originate from a neighboring jurisdiction show real similarity with the vehicles that were recovered from the lake and the investigation is proceeding along those lines," the sheriff's office said in a statement. "However, no positive identification has been made."

Custer County Sheriff Bruce Peoples said one of the cars might belong to Jimmy Williams, 16, who was reported missing in 1970. His car was a 1969 blue Chevrolet Camaro, which looked similar to one of the cars that were recovered.

He was last known to be driving around with his friends Thomas Rios, 18, and Leah Johnson, 18, and none of them have been seen since.

"This very well may be the car with three missing teens from Sayre in 1970," Peoples told ABC News' Oklahoma City affiliate KOCO-TV. "We have some indication that the other vehicle is one that was reported missing in 1969."

Police said the Oklahoma State Medical Examiner's Office will take possession of the remains and possibly try to match DNA to known surviving family members.

"It's closure for those families that no longer have to wonder what happened to their loved ones and that's one of the reasons, of course, we investigate this, to determine if a crime was committed," Peoples said.